Adipose tissue contains a cell population of large, lipid-filled adipocytes and a population of non-adipocyte cells, which comprises cells associated with various connective fibres and cells associated with capillaries and larger blood vessels. The non-adipocyte cell population also comprises a variety of infiltrating immune cells and cells and cell processes associated with the nervous system. The non-adipocyte cell population is also thought to comprise a population of adipose-derived adult stem cells and consequently there has been interest in using adipose tissue as a source of isolated adult stem cells for various therapeutic applications.
In general, methods for obtaining adipose tissue-derived presumptive adult stem cells involves depleting adipocytes from adipose-derived non-adipocyte cells, which requires digesting adipose tissue with enzymes such as collagenase, and then separating the liberated cells by centrifuging the digested sample. During centrifugation, the adipose-derived non-adipocyte cells separate from the adipocytes to form a pellet, whereas the lipid containing adipocytes float. The fraction containing the non-adipocyte cells is then used as a source of tissue stem cells.